Used off of ebay. If buying used, best to have measurements and pictures readily available.
What model Bolens?
It appears MTD took over Bolens so there has to be aftermarket parts available.
I have a H16XL tractor deck sitting around so used parts are out there. There are several rider salvage yards across the US. Most sell off of Ebay.
If it is just a bearing you need, then that might be a less expensive route to repair.